It is known that polymers can be rendered flame-retardant using halogen-containing additives or comonomers, where appropriate, combined with antimony compounds. Flame retardants based on metal hydroxides, such as Al(OH).sub.3 or Mg(OH).sub.2, are generally insufficiently active and/or impair the mechanical properties of the polymer because the amount used is high. Phosphorus-containing flame retardants, e.g. ammonium polyphosphate, used alone, also has relatively low activity per se, compared with halogen compounds.
Particular requirements are placed on flame retardants for aqueous polymer dispersions: they must be water-soluble or water-dispersible, and the dispersion in which the flame retardant is present must be stable, i.e. there must be no flocculation or coagulation, and the flame retardant must be stable in, and homogeneously distributed in, films prepared from the dispersion.
DE 3803030 C2 describes the use of phosphonates as flame retardants in plastics, such as polyurethane, polyvinyl chloride, polyester and epoxy resin.
EP 0733638 A1 describes phosphorus-containing aromatic dicarboxylic esters as halogen-free flame retardants for polyester fiber materials.
DE-A 19508530 describes the simultaneous use of functionalized monomers and phosphorus compounds reactive with these functional groups to improve flame retardancy in aqueous dispersion compositions.
U.S. Pat. No. 5,412,014 A describes a process for rendering thermoplastics or heat-curable resins flame-retardant using a mixture of a silicone polymer powder composed of a polydiorganosiloxane and silica, together with a phosphorus-containing flame retardant.